One embodiment relates to a method for sidelink related operation of a receiving (RX) user equipment (UE) in a wireless communication system, the method comprising the steps in which: the RX UE receives first SCI from a transmitting UE (TX UE) through a physical sidelink control channel (PSCCH); and the RX UE receives a physical sidelink shared channel (PSSCH) and second SCI from the TX UE on the basis of the first SCI, wherein the second SCI includes information about activating physical sidelink feedback channel (PSFCH) transmission related to the PSSCH, and whether to start a retransmission timer on the basis of the PSFCH transmission being dropped is determined on the basis of whether the dropped PSFCH transmission is related to either NACK or ACK.